So, I've searched through the forums to get the general opinion on transmission coolers and the consensus is it's a good idea. My question is, can I bypass my radiator entirely by putting in a transmission cooler? I live in Northern NY and it gets cold up here in the winter (-15F), so my only worry is the transmission fluid being cooled too much in the winter months. I'm currently battling a slow leak at the inlet of the radiator for the transmission fluid and I'd like to cut it out of the picture completely. Any insight that keeps me from breaking out the Fundamentals of Heat and Mass Transfer book on my shelf would be greatly appreciated. Thanks!

 

yes you can bypass your radiator trans cooler with an external cooler and i have never personally heard of trans fluid being to cold causing an issue

 

That shouldn't cause any issues. I'd go with a bit larger model than the smallest being you won't have the radiator doing any cooling. Heat is the enemy of automatic transmissions, not cold.